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Bureau of Mines Information Circular/1987 



Test Apparatus for Measuring 
Sound Power Levels of Drills 



By William W. Aljoe, Robert R. Stein, 
and Roy C. Bartholomae 




UNITED STATES DEPARTMENT OF THE INTERIOR 




/>j2jfc> j&jj* , jVu^^/j/i^ 



Information Circular 9166 

A 




Test Apparatus for Measuring 
Sound Power Levels of Drills 



By William W. Aljoe, Robert R. Stein, 
and Roy C. Bartholomae 



UNITED STATES DEPARTMENT OF THE INTERIOR 
Donald Paul Hodel, Secretary 

BUREAU OF MINES 

David S. Brown, Acting Director 










Library of Congress Cataloging in Publication Data: 



Aljoe, William W. 

Test apparatus for measuring sound power levels of drills. 

(Information circular/United States Department of the Interior. Bureau of Mines; Hltib) 

Bibliography: p. 34-35. 

Supt. of Docs, no.: I 28.27: 9166. 

1. Rock-drills— Noise. I. Stein, Robert R. II. Bartholomae. R. C III Title IV. Series: 
Information circular (United States. Bureau of Mines): 9166. 



TN295.U4 [TN279] 



622 s 



[622'.8] 87-600273 









CONTENTS 

Page 

Abs t ract 1 

Introduction 2 

Test system considerations 4 

Control of drill operating parameters 4 

Control of the acoustical environment 5 

Data collection and analysis 7 

System description 8 

System operation 12 

Drill test program 12 

Test sequence 12 

Data input and startup procedure 13 

Data collection and display 14 

Control subsystems 15 

IBM-XT microcomputer 15 

Westinghouse PC-700 process controller 15 

Drill rig positioning control 16 

Carriage lock control 16 

Feed thrust and hole depth control 17 

Drill hammer control 18 

Drill rod rotation control X 18 

Flushing water control 20 

Other drill test commands 20 

Hole location program 21 

Selection of hole position 21 

Validation of input data 22 

Selection of hole depth 22 

Data analysis program 22 

Direct data analysis and graphics 23 

Test selection 23 

Raw data retrieval 23 

Basic system graphics 25 

Expanded data analysis through spreadsheets 27 

File conversion procedure 27 

Advantages of spreadsheet analysis 28 

Initial test results 29 

Pneumatic versus hydraulic percussion drills 30 

Rotary versus percussion drills 32 

Discussion 34 

References 34 

ILLUSTRATIONS 

1. Noise sources on typical hand-held percussion drill 2 

2. Noise sources on typical jumbo-mounted percussion drill 3 

3. Typical noise radiation pattern 6 

4. Components of automated drill test fixture and control system 8 

5. Drill test rig in reverberation chamber, top view 10 

6. Drill test rig in reverberation chamber, profile view 10 

7. Drill test rig in reverberation chamber, rear view showing control room.... 11 

8. Drill test rig in reverberation chamber, control valves and process 

sensors 11 

9. Drill test software program selection menu 12 



11 



ILLUSTRATIONS— Continued 



Page 



10. Main data input menu for drill test program 

11. Drill rig carriage and boom positioning system 

12. Drill carriage lock system 

13. Feed thrust and hole depth control system 

14. Drill hammer control system 

15. Drill rod rotation control system 

16. Data input menu for hole location program 

17. Data input menu for analysis program 

18. Printout of drill test data 

19. Graphs of hammer pressure, feed thrust, feed rate, and sound power versus 

elapsed time 

20. Sound power spectrum and spectrum waterfall graphs 

21. Data input menu for Spreadsheet Formatter program 

22. Average frequency spectra: pneumatic and hydraulic percussion drills 

23. Frequency spectra for percussion drills, beginning versus end of hole 

24. Average frequency spectra: pneumatic and hydraulic percussion drills, 

pneumatic rotary drill 

25. Frequency spectra for pneumatic rotary drill: beginning versus end 

TABLE 

1. Maximum values and accuracy of ADTF control parameters 



13 

16 
17 
17 
19 
20 
21 
23 
24 

25 
26 
27 
30 
31 

33 
33 



13 





UNIT OF MEASURE ABBREVIATIONS 


USED IN 


THIS REPORT 


cfm 


cubic foot per minute 


in/s 


inch per second 


dB 


decibel 


Kb 


kilo byte 


dBA 


decibel, A-weighted 


kHz 


kilohertz 


ft 


foot 


lbf 


pound (force) 


ft 2 


square foot 


Mb 


megabyte 


ft 3 


cubic foot 


min 


minute 


f t/min 


foot per minute 


pet 


percent 


gpm 


gallon per minute 


psi 


pound (force) per 
square inch 


h/d 


hour per day 










s 


second 


Hz 


Hertz 










V 


volt 


in 


inch 







TEST APPARATUS FOR MEASURING SOUND POWER LEVELS OF 

DRILLS 

By William W. Aljoe, 1 Robert R. Stein, 1 and Roy C. Bartholomae 2 



ABSTRACT 

This Bureau of Mines report describes in detail the design and opera- 
tion of a test apparatus for measuring the sound power levels of drills 
used by the mining industry. The two major components of the test ap- 
paratus are a computer-controlled automated drill test fixture (ADTF) 
and a large (45,000-ft 3 ) reverberation chamber that houses the ADTF. 
Design specifications and performance capabilities of the ADTF and the 
reverberation room are given. Initial test results for three types of 
drills — a pneumatic percussion drill, a hydraulic percussion drill, and 
a pneumatic rotary drill — are given to illustrate the types of experi- 
ments that can be conducted with the test appartus. 



1 Mining engineer. 
^Supervisory electrical engineer. 
Pittsburgh Research Center, Bureau of Mines, Pittsburgh, PA. 



INTRODUCTION 



Percussion drills used in the mining 
industry produce noise that can cause 
exposures of 10 to 20 times the limits 
allowed by Federal noise regulations. 
Typical noise levels experienced by per- 
cussion drill operators are 110 to 120 
dBA. Approximately 60, 000 percussion 
drills are being used in the mining in- 
dustry (JO, 3 and many more are used in 
the construction industry. Given the 
severity of the percussion drill noise 
problem, it is not surprising that con- 
siderable efforts have been made toward 
its control. 

The primary noise-generating mechanism 
in all percussion drills is the repeated 
hammering action of an oscillating steel 
piston on the end of a long, slender 
striking bar (drill rod). This action 
causes vibration of both the drill rod 
and the cylindrical piston housing, 
thereby producing drill rod noise and 
drill body noise. On pneumatic drills, 
the high-pressure air used to oscillate 
the piston is exhausted to the atmosphere 
through ports in the drill body, thus 
producing air exhaust noise. Figure 1 
depicts these three major noise sources 
on a typical hand-held pneumatic (stoper) 
drill. Figure 2 shows the various noise 
sources associated with a typical 
machine-mounted (jumbo) drill; however, 
the drill body, drill rod, and air ex- 
haust are still by far the most serious 
noise sources on the drill. 

Numerous attempts have been made in the 
past by the Bureau of Mines and other re- 
searchers to control percussion drill 
noise through the use of retrofit noise 
control treatments (_2-_6_) and new drill 
design features (7-10). These attempts 
have been moderately successful, result- 
ing in noise reductions of up to 15 dBA 
at the drill operator position. Unfortu- 
nately, some of the noise-controlled 
drills were rather impractical from an 
operation standpoint (e.g., reduced 
drilling rates, muffler freezing, exces- 
sive weight and bulk). 

■^Underlined numbers in parentheses re- 
fer to items in the list of references at 
the end of this report. 



Pr 



Drill steel 




FIGURE 1. — Noise sources on typical hand-held percussion 
drill. 



Piston-striking bar impact 

Leakage air noise 

Air motor noise 
^ , Body noise 

■ Exhaust noise 




FIGURE 2. — Noise sources on typical jumbo-mounted percussion drill. 



Furthermore, in most cases the quieted 
noise levels were still above 100 dBA; 
operator exposure would have to be lim- 
ited to only 2 h/d to maintain compliance 
with Federal noise regulations. 

To date, the most effective means of 
protecting the percussion drill operator 
from noise overexposure has been to iso- 
late him or her from the noise source by 
using an acoustical cab. Noise reduc- 
tions of up to 20 dBA have been achieved 
through this technique, and in several 
cases the noise level measured inside the 
cab was below 90 dBA (6). Acoustical 
cabs can be applied most successfully to 
machine-mounted drills that are used in 
areas of unrestricted headroom or where 
remote control of drill positioning and 
operation is employed. However, many 
mining situations require the use of 
small hand-held drills because of space 
limitations; this precludes the use of 
acoustical cabs. In fact, the hand-held 
percussion drill remains the bulwark of 



many underground ore mining operations 
because of its compactness, flexibility, 
reliability, and low cost. Space limita- 
tions and interference with drill opera- 
tion (e.g., operator vision) also dis- 
courage the use of acoustical cabs on 
many types of jumbo-mounted drills. 

Considering the high-energy nature of 
percussion drilling, the limited success 
of previous efforts to control drill 
noise at its source, and the limited 
practical application of acoustical cabs, 
it is doubtful that the majority of per- 
cussion drill operators will work, in a 
nonhazardous noise environment in the 
near future. If the mining industry con- 
tinues to use percussion drills, even 
quieted models, as it has in the past, it 
is reasonable to assume that numerous 
noise overexposures will occur in the 
years to come. 

Despite the severity of the percussion 
drill noise problem and the fact that all 
percussion drills are inherently noisy, 



it is important to note that some drills 
generate more noise than others. Opera- 
tor exposure to noise can be reduced by 
choosing a less noisy drill or drilling 
system. Factors that can affect the 
noise produced by a drill include the 
source of power (air or hydraulic), input 
energy, degree of wear and leakage, drill 
rod size and type, hammer and shank con- 
figuration, means of drill steel rotation 
(rifle bar or independent), and location 
of the operator with respect to the 
drill. The application and effectiveness 
of noise control techniques are greatly 
affected by these differences. 

An in-depth understanding of drill de- 
sign characteristics and their effect on 
noise is an important part of any effort 
to reduce the noise problem. The Bureau 



of Mines, while continuing in this en- 
deavor, does not possess the funding or 
drill design expertise to embark on a 
program to develop a drill or drilling 
system that can solve the problem com- 
pletely. However, with the aid of the 
test apparatus described in this report, 
it is possible for the Bureau to signifi- 
cantly enhance the body of knowledge on 
the subject of drilling noise. For ex- 
ample, the test apparatus can provide 
valuable but heretofore unavailable quan- 
titative information on the sound power 
levels produced by different types and 
models of drills. Noise variations re- 
sulting from differences in drill operat- 
ing parameters can also be investigated 
and quantified. 



TEST SYSTEM CONSIDERATIONS 



To conduct thorough, systematic studies 
of drill noise, the researcher needs (1) 
control of the parameters that affect 
drill performance, (2) control of the 
acoustical environment in which the drill 
operates, and (3) a comprehensive, well- 
organized data collection and analysis 
system. The Bureau's test apparatus ful- 
fills all three of these requirements. 

CONTROL OF DRILL OPERATING PARAMETERS 

The operation of a percussion drill is 
affected by many parameters such as the 
composition of the drilling medium, 
sharpness of the bit, type of bit used, 
length and type of drill rod, number of 
rod sections, drill feed force, supply 
pressure to the drill, wear condition of 



the drill, and hole flushing medium. Un- 
der actual drilling conditions in the 
field, control of all these parameters is 
a very difficult and sometimes impossible 
task. In short, it can be said that no 
two holes drilled in the field are ever 
exactly the same. 

In the laboratory, however, it is pos- 
sible to control these parameters such 
that any drilled hole is repeatable. 
More importantly, it is possible to se- 
lectively change only one parameter from 
hole to hole to determine its effect on 
noise and penetration rate. The computer 
controlled automated drill test fixture 
(ADTF) facilitates this process by auto- 
matically maintaining the supply pres- 
sure, rotation flow, and feed force spec- 
ified by the user. These parameters can 



also be changed by the user during the 
course of a test if desired. The ADTF 

also allows the user to select an exact 
hole location (following a preprogrammed 
pattern), hole depth, and drill power 
source (air or hydraulic) for each test. 

The ADTF achieves this control through 
the use of standard, commercially- 
available hardware such as pressure, 
flow, and position transducers, a pro- 
grammable process controller, and a desk- 
top microcomputer. Software designed 
specifically for the purpose of drill 
test provides the user with continuous 
on-line information and interactive capa- 
bility via the computer's cathode ray 
tube and keyboard. Safety is ensured by 
the presence of several types of auto- 
matic and user-initiated shutdown modes. 

By conducting drill noise tests in the 
laboratory, it is also possible to exer- 
cise almost complete control of the 
drilling medium, bit type and sharpness, 
drill rod length and type, and hole 
flushing medium. These parameters can 
almost never be changed or controlled in 
the field due to local geology, blasthole 
size requirements, and other production 
considerations. The capability of pro- 
viding a relatively homogeneous drilling 
medium (precast concrete or precut gran- 
ite) is particularly advantageous when 
assessing the effect of other drilling 
parameters on drill penetration rate. 

CONTROL OF THE ACOUSTICAL ENVIRONMENT 

The acoustical environment of an oper- 
ating mine is rarely consistent because 
the extent of the mine and the location 
of the noise sources change almost daily 
as mining progresses. 

Irregular reflecting surfaces are often 
present, and extraneous noise sources 
(other pieces of mining equipment) add to 
the difficulty of measuring the noise 
produced by a drill. Microphone location 



is another important factor to consider 
when measuring drill noise in the field 
because the sound pressure can vary 
greatly from point to point within the 
area of interest. Measurement of drill 
noise in the laboratory allows for con- 
trol of some of these variables, but the 
experimental environment must be chosen 
carefully to assure that useful noise in- 
formation is obtained in a practical and 
cost-effective manner. 

The two fundamental properties that de- 
fine the noise-radiating capability of a 
sound source are its sound power and di- 
rectional characteristics. Sound power 
is a measure of the rate at which acous- 
tical energy is emitted by a noise 
source; it is usually expressed as sound 
power level, in decibels (dB), by the 
formula 

PWL = 10 log (W ac + /W ref ), 

where PWL = sound power level, dB, 

W act = actual sound power, w, 

and W re f = reference sound power, 
10~ 12 w. 

The most important distinction between 
sound power level and sound pressure 
level, the quantity most commonly asso- 
ciated with noise, is that sound power 
is a fundamental property of the noise 
source itself. Conversely, the sound 
pressure level is dependent on the 
distance from the noise source, the 
direction from the source, and the acous- 
tical properties of the environment in 
which it is measured. The relationship 
between sound pressure and sound power 
levels can be quantified (11): 

SPL = PWL + 10 log [(Q/4 a r 2 )+(4/ a S)] 
+ 10, 



where SPL = sound pressure level at any 
given point in an 
environment , dB , 

PWL = sound power level of noise 
source, dB , 

Q = directivity factor (dimen- 
sionless) of the source, 
whose value is dependent 
on the angle from the 
acoustical center of the 
source to the measurement 
point, 

r = distance from the source, 
ft, 

a = average absorption coeffi- 
cient (dimensionless ) of 
the acoustical environment, 
including its boundaries 
and objects located within 
it, 

and S - total surface area, ft 2 , of 
all reflecting surfaces 
within the environment. 



For the drill noise research program 
envisioned by the Bureau of Mines, sound 
power is the quantity of greatest inter- 
est because (1) it allows direct noise 
comparisons to be made among different 
types and models of drills, and (2) it 
can be used to predict the sound pressure 
levels that will occur in other envi- 
ronments, given their acoustical 
characteristics. 

The directional property of a sound 
source describes its tendency to radiate 
more noise in one direction than in 
others. Directional properties are usu- 
ally displayed in a graphical form called 
a radiation pattern (fig- 3), showing 
sound pressure level at a fixed distance 
from the source as a function of angle. 
It should be noted that figure 3 is for 
illustrative purposes only; the sound 
pressure levels in the figure do not cor- 
respond to measured values for an actual 
drill. 

From a purely diagnostic standpoint, 
the most complete characterization of any 
noise source can be obtained by isolating 
it in an anechoic (free field) environ- 
ment, i.e., one in which no reflections 



50 c 



ANGLE FROM NOISE SOURCE 
60° 70° 80° 90° 100° 110° 120° 



I30 ( 



UJ 




o 




a: 




ID 
O 


40° 


CO 




UJ 




CO 




o 


30° 


2 




S 




o 


20° 


u_ 




iii 




_i 


10° 


o 




z 




< 


0° 




100 



90 80 Noise source 80 90 

SOUND PRESSURE LEVEL, dB 

FIGURE 3.— Typical noise radiation pattern. 



100 



occur and no other noise sources are 
present. By measuring the sound pressure 
at numerous points on a series of imagin- 
ary spheres located at various radial 
distances from the geometric center of 
the noise source, it is possible to 
determine both the sound power and the 
directional properties of the source. 
Unfortunately, this experimental approach 
could not be pursued by the Bureau of 
Mines because it would have been prohibi- 
tively expensive, time consuming, and 
impractical. 

In terms of cost, practicality, and the 
ability to obtain useful information on 
drill noise, the Bureau of Mines deter- 
mined that the reverberant environment 
was the best environment to choose. An 
important feature of a perfectly rever- 
berant environment is that the sound 
pressure levels at all points are the 
same due to the multitude of sound re- 
flections that occur at its boundaries 
(walls). If only one dominant sound 
source is present in the environment, its 
sound power level can be calculated easi- 
ly by comparing the measured sound pres- 
sure levels to those produced by a refer- 
ence source of known sound power. Most 
importantly, it was possible to con- 
struct, at a reasonable cost, a reverber- 
ant environment (reverberation chamber) 
capable of housing a full-sized drill 
test fixture. In addition, the instru- 
mentation needed to automatically calcu- 
late drill sound power levels was afford- 
able, the test procedures involved with 
this setup were relatively simple, and 
useful results could be obtained within a 
reasonable time frame. 

The greatest disadvantage of testing 
drills in a reverberant environment is 
the inability to determine the direction- 
al nature of the noise source. The lack 
of directional information makes it more 
difficult to assess the relative noise 
contributions of the drill rod, drill 
body, and air exhaust. Also, potential 



noise reductions that could result from 
the judicious selection of the drill 
operator position or the insertion of 
partial acoustical barriers between the 
drill and the operator cannot be de- 
tected. This disadvantage can be over- 
come by conducting supplemental tests in 
a semifree field (outdoors) with drills 
that exhibit particularly strong direc- 
tivity patterns. 

DATA COLLECTION AND ANALYSIS 

Collection of drilling data in the 
field usually requires substantial human 
effort such as constant visual monitoring 
of pressure gauges, flowmeters, stop- 
watches, etc. Noise monitoring in the 
field is often performed only with hand- 
held sound level meters. Extensive, 
careful notes must be maintained to make 
sure the data are recorded completely and 
correctly. Even when data are recorded 
electronically (strip chart recorders, 
data loggers, or magnetic tape), consid- 
erable human intervention is needed to 
assemble and correlate the data for later 
analysis. 

The computer-controlled ADTF is the 
ideal means for simplifying the task of 
data collection and analysis. Signals 
from permanently installed transducers 
for flow, pressure, and position are con- 
verted by the ADTF software into standard 
units (cfm, psi, etc. ) and are recorded 
on a floppy disk at 4-s intervals. Sound 
power levels are recorded at 18-s inter- 
vals, and a continuous record of time 
elapsed during the test allows for auto- 
matic correlation of all test parameters. 
All other information pertinent to the 
test (drill type, hole size and location, 
drill rod and bit type, etc. ) is also 
recorded on disk, and the computer as- 
signs a specific test number to the en- 
tire block of test data. This greatly 
facilitates posttest analysis and 
comparisons among different tests. 



SYSTEM DESCRIPTION 



The drill noise test apparatus consists 
of eight distinct components, shown sche- 
matically in figure 4: 

1. A microcomputer (IBM model PC -XT, 4 
referred to as the XT) with hard-disk 
storage of menu-driven programs for drill 
operation and data analysis. 

2. A programmable process controller 
(Westinghouse PC-700, referred to as the 
PC) with control cards for input, output, 
and high-speed counting functions. 

3. A 15-ft-long by 9-ft-wide by 
6-ft-high drill test rig consisting of 

^Reference to specific products does 
not imply endorsement by the Bureau of 
Mines. 



(a) a rubber-tired carriage, (b) a pivot- 
ing boom with two 10-ft-long feed chan- 
nels, (c) the drills themselves, and (d) 
the hydraulic and pneumatic control 
valves and transducers. Figures 5-8 show 
several views of the drill test rig and 
drilling medium. The valves and trans- 
ducers (fig. 8) are designed to meet the 
capacities of the hydraulic and pneumatic 
power sources listed in items 6 and 7 
below. 

4. Valve driver cards (manufactured by 
Ledex, Inc. , and referred to as the Ledex 
drivers) needed to operate some of the 
larger hydraulic control valves that re- 
quire a 24-V input potential. 



Control 
room 



O 

o o 



r 



Hydraulic power supply 
control box 



[—Hydraulic power supply 
control cable 



I | /-Micro- 
Z~~_ computer 



ff 



Process controller (PC) 



1- 



¥ 



± 



Sound-measuring instrumentation 



Frequency-to-analog 
converter cards 



2l 



High-speed counters 
Output cards 
Input cards 

J-±I5.8-V power supply \J 

5-V power supply 
/ — PC output cable 




24-V 

power 

supply 



-Test chamber 
(reverberation 
room) 




Valve-driver and PC output cables 



t: 



A 



Input signal cable Water supply 

FIGURE 4. — Components of automated drill test fixture and control system 



Hydraulic lines (2) 
-Compressed air line 

Hydraulic power supply 



5. A sound measurement system consist- 
ing of an array of microphones suspended 
from the ceiling of the reverberation 
room and instrumentation to calculate 
sound power levels. Figure 7 shows some 
of the sound measuring instrumentation in 
the control room adjacent to the rever- 
beration chamber. 

6. A remotely controlled hyraulic 
power source capable of providing up to 
35 gpm of flow at 5,000-psi pressure. 
This is sufficient to operate most cur- 
rently available hydraulic percussion 
drills. 

7. A compressed air source capable of 
providing 1,200 cfm of flow at 100-psi 
pressure. This is sufficient to operate 
most currently available pneumatic drills 
with the exception of down-the-hole 
drills. 

8. A flushing water source for dust 
suppression. 

The first four components combine to 
form the automated drill test fixture 
(ADTF); the other four provide vital sup- 
port functions and are accessed by the 
ADTF during its operation. The drilling 
rig and microphones are located inside 
the reverberation chamber, the XT and 
sound measuring instrumentation are lo- 
cated inside the control room adjacent to 
the chamber, and the PC and valve drivers 
are located in cabinets immediately out- 
side both the test chamber and control 
room. The hydraulic power pack and air 
compressor are located remotely so that 
their noise contribution to the test 
chamber is minimal. 

All eight components are required for 
the operation of pneumatic drills, and 
all but the air compressor are required 
for hydraulic drills. Although two 
drills can be mounted on the ADTF at 
once, only one drill at a time can be 
operated. The advantage of having two 
feeds is that a pneumatic and hydraulic 
drill can operate in consecutive tests 



without having to dismantle and reconnect 
numerous fluid supply connections. Both 
percussive-rotary and all-rotary drills 
can be tested on the ADTF using the same 
test program and procedures. 

The primary drilling medium consists of 
two 6- by 6- by 12-ft concrete blocks 
(compressive strength approx. 6,000 psi) 
inserted into the chamber wall; see fig- 
ures 5 and 6. Provision has also been 
made to drill into granite or another 
drilling medium either by replacing the 
concrete or by inserting the medium into 
the wall between the two concrete blocks. 
All drilling takes place in the horizon- 
tal direction, with a maximum depth of 12 
ft governed by the confines of the build- 
ing in which the reverberation chamber is 
housed. 

The reverberation chamber and sound 
measurement system meet the criteria of 
ANSI SI. 31-1980, "Precision Methods for 
the Determination of Sound Power Levels 
of Broad-Band Noise Sources in Reverbera- 
tion Rooms." The chamber itself is 60 ft 
long by 34 ft wide by 22 ft high and is 
constructed of filled concrete block with 
nonabsorptive paint covering its interior 
surfaces. Exhaust fans and floor drains 
provide a clean working environment with 
consistent acoustical properties. The 
sound measurement system consists of (1) 
an array of 20 randomly spaced micro- 
phones positioned at 9 to 11 ft above the 
chamber floor, (2) two 8-channel multi- 
plexers (Bruel & Kjaer model 2811) to 
provide access to 16 of the 20 micro- 
phones during any single test, and (3) a 
Bruel & Kjaer model 7507 sound power 
calculator. Alternatively, if sound 
pressure rather than sound power were the 
desired quantity, a Bruel & Kjaer model 
2131 digital frequency analyzer could 
serve as the third component of the sound 
measuring system. This system was 
qualified using the test procedures in 
section 8 of the ANSI SI. 31-1980. 



10 




FIGURE 5.— Drill test rig in reverberation chamber, top view. 




FIGURE 6.— Drill test rig in reverberation chamber, profile view 



11 




FIGURE 7.— Drill test rig in reverberation chamber, rear view showing control room. 







FIGURE 8. — Drill test rig in reverberation chamber, control valves and process sensors. 



12 



SYSTEM OPERATION 



The operator activates the drill test 
system by turning on the process control- 
ler (PC), the sound power measurement 
system, and the microcomputer (XT). 
Turning on the XT with no floppy disk in 
place automatically loads the disk oper- 
ating system (DOS) from the hard disk. 
At the DOS prompt, the operator loads the 
drill test software and is presented with 
the menu shown in figure 9.5 The func- 
tion keys Fl through F6 on the XT key- 
board are used to access the various op- 
tions. The three major elements of the 
drill test software — the drill test pro- 
gram, analysis program, and hole location 
program — are described in this section. 

DRILL TEST PROGRAM 

Test Sequence 

Prior to running a drill noise test, 
the operator starts the hydraulic power 
pack and air compressor (if required) and 
adjusts them to operating pressures that 
are at least as great as those that will 
be required for the test. A typical 
drill noise test sequence follows: 

1. The test operator loads the drill 
test program (Fl in figure 9) and enters 
descriptive information and control para- 
meters (set points) into the XT. 

2. The drill test program checks the 
input values and, if consistent with sys- 
tem limitations, loads them into the PC 
along with a command word to start the 
test. 

3. The PC moves the drilling rig to 
the selected hole location, locks the 
carriage, and pauses for an operator com- 
mand to proceed. When this command is 
issued, the PC starts the drilling pro- 
cess, and the sound measurement system is 
activated. Throughout the test, the PC 
handles the task of reading the pressure 
and flow transducers, comparing their 
values to those of the set points, and 

^Throughout this report, graphs and 
menus such as figure 9 have been modified 
slightly to conform to Bureau of Mines 
publication standards. 



opening or closing valves to maintain the 
set points as closely as possible. 

4. When the feed thrust reaches the 
set point, the XT starts to collect in- 
formation from the PC at intervals speci- 
fied by the test operator. It continues 
to do so until the hole depth reaches the 
set point or the operator terminates the 
test. At this point the XT instructs the 
PC to stop drilling and retract the 
drill; the sound measurment system is 
also deactivated, and the data are 
written to a file on a floppy disk in the 
A: disk drive unless the operator de- 
cides the test was invalid. 

5. When the drill reaches its origi- 
nal, completely retracted position, the 
system waits for a new test command to be 
entered into the XT. 

6. The operator either analyzes data 
from the test just completed or enters 
new data for another test. If no other 
tests are needed but data analysis is de- 
sired for one or more previous tests, the 
operator exits the drill test program, 
enters the data analysis program (F2 in 
figure 9), and calls in the desired test 
numbers. Pressing the F4 key allows the 
operator to check the directory of the 
disk in the A: drive. 

7. If no subsequent tests or data 
analyses are desired, the operator issues 
a command that moves the rig to a home 
position (conveniently located to permit 
drill maintenance or removal), exits the 
drill test program, and shuts down the 
ADTF and power sources. 



Choose option : 

Fl - Drill test program 

F2 - Analysis program 

F3 - Hole location program 

F4 - Directory of tests on A : 

F5 - Edit controls file ff 

F6 - Exit to DOS 



FIGURE 9. — Drill test software program selection menu. 



13 



Data Input and Startup Procedure 

Data input begins when the operator en- 
ters the drill test program and is pre- 
sented with the menu shown in figure 10. 
The circled numbers in figure 10 denote 
the fields in which test data are entered 
by the operator, as described below: 

Fields 1, 4, 5, 6, and 9 are text en- 
tries for documentation purposes; they 
facilitate later analysis but do not di- 
rectly impact the test itself. 

Field 2, entered as P or H, identifies 
whether the drill to be tested is pneu- 
matic or hydraulic. Field 3, entered as 
1 or 2, identifies the feed channel on 
which the test drill is mounted. This 
information allows the appropriate set of 
control cards in the PC to be activated 
during the test. 

Fields 7 and 8, respectively, specify 
the vertical (rows A through N) and 
horizontal (columns 1 through 36) hole 
location. Field 3 is also important in 
this regard because, for the same hole 
location on the wall, the actual amount 
of carriage and boom movement is dif- 
ferent for each feed. The operation of 
the hole location program is discussed in 
more detail later in this report. 

Fields 10, 11, 12, and 13 are the main 
control parameters governing the 
operation of the drill during the test. 



Input values are assigned the units shown 
in figure 10. In the case of field 12, 
rotation flow, the units depend on field 
2; gpm Is assumed for hydraulic drills 
and cfm for pneumatic drills. Table 1 
lists the maximum allowable values of 
these parameters and the accuracies 
achieved by the ADTF control system. 

After all data have been entered, the 
operator presses the F9 function key 
(fig. 10) to continue the test. The pro- 
gram checks the input values for confor- 
mance with the above requirements, issues 
an error message if this is not the case, 
and allows the operator to correct the 
erroneous data. If the inputs are valid, 
the program loads the input values into 

TABLE 1. - Maximum values and accuracy 
of ADTF control parameters 



Parameter 


Maximum 


Accuracy 




value 


pet 


Hammer pressure 


5,000 psi 


5 


(hydraulic). 






Hammer pressure 


350 psi 


5 


(pneumatic). 








12,000 lbf 


4 


Rotation flow 


50 gpm 


5 


(hydraulic). 






Rotation flow 


1,000 cfm 


2 


(pneumatic). 






Distance drilled... 


144 in 


3 



Executive 
commands 



Test docu-. 
mentation 



F I Exit program 

F3 Move platform home 

F9 Start test 



Main menu 



F2 Master reset 

F4 Test without move 

FIO Data analysis 



(D Drill tested : 
© Hole size : 
-(ZHD Location : 



(D Pneumatic or hydraulic; 
® Drill steel : 
(D Comments 1 



Date : September 15, 1985 
Time; 13=18=35 
Run; XXXX 



(3) Feed = 
(6) Bit type = 



Control 
parameters 



® Operating hammer pressure 

(D) Feed thrust 

@ Rotation flow* 

© Distance drilled 



Set Actual Status 0001 1000 0000 0000 

psi XXXX Test stage 

lbf XXXX Elapsed time .... 

g/cf XXXX Drill frequency .... BPM 

in XXXX Sound power .... dB 



♦The notation g/cf for rotation flow reflects the 
fact that flow is measured in gpm for hydraulic 
drills and cfm for pneumatic drills. 



On-line information 



FIGURE 10.— Main data input menu for drill test program. 



14 



the PC, issues a "Ready" message, and 
prompts the operator to press F9 again. 
The drilling rig then moves out to the 
specified hole location, locks itself in- 
to place with two clamping cylinders, and 
pauses. The hole location is then 
checked visually and, if satisfactory, 
the operator presses F9 a third time to 
start the drilling process. At any time 
during the startup procedure or drilling 
process, the operator can press the [Esc] 
key, standard on all IBM and IBM- 
compatible personal computer keyboards, 
to halt the test and enter new input data 
into the main menu. A closed-circuit 
television system enables the operator to 
monitor the entire sequence from the 
safety of the control room and allows him 
or her to terminate the test quickly 
should problems occur. 

Data Collection and Display 

As soon as the drill test program 
checks the data input values and finds 
them to be valid, it opens a file on the 
XT floppy disk and writes the input data 
to the file. These drill test files are 
named "TEST .DAT", with the blank cor- 
responding to the sequential test number 
assigned by the drill test program. This 
four-digit test number is then displayed 
on the XT video monitor ("Run" in figure 
10) and is used for all subsequent data 
retrieval and analysis. 

After drilling has begun, control of 
the test is maintained by the process 
controller (PC). As soon as the feed 
thrust reaches its set point, the XT col- 
lects data by reading the PC and the 
sound measuring instrumentation at speci- 
fied intervals and writing this informa- 
tion to the floppy disk file. The opti- 
mum sampling interval for data collected 
from the PC was found to be 4 s. Shorter 
intervals are possible but would result 
in rapid exhaustion of floppy disk space; 
longer intervals could result in the loss 
of important test data. The sampling in- 
terval for sound power data was chosen to 
be 18 s. This interval allows the multi- 
plexer to scan 16 microphones for 1 s 
each and gives the sound power calculator 
ample time to perform its computations 
and store the data. These intervals, 



along with the maximum control parameter 
values listed in table 1, can be changed 
easily by the test operator. The F5 
"Edit conrols file" key in figure 9 pro- 
vides the operator with a menu that 
enables these changes to be made from the 
XT keyboard. Selected information is 
also displayed on the XT video monitor, 
as shown in figure 10. The data dis- 
played immediately to the right of fields 
10 through 13 allow the operator to com- 
pare the actual values of the control 
parameters with those of the set points. 
The lower right section of figure 10 con- 
tains the following information: 

Status word. — This 16-digit binary 
number contains information pertinent to 
the movement and locking of the drill 
test rig. It changes during the drill 
movement sequence, with each digit either 
identifying the status of a particular 
hardware component critical to this pro- 
cess (e.g., limit switches open or 
closed, input parameters valid or not) or 
issuing a command to proceed to the next 
step in the movement cycle (e.g., move 
carriage and boom to set point, lock car- 
riage). The status word is a valuable 
troubleshooting aid if the drill rig 
either fails to move on command or moves 
incorrectly. 

Test stage. — A string of text charac- 
ters written to the display on the basis 
of the status word. The four test stages 
are collaring (drill rig moving to set 
point and drill operating before feed 
thrust reaches set point), testing (data 
being collected), retracting, and moving 
home. 

Elapsed time. — The PC timer starts 
when the feed thrust reaches the set 
point and ends when the prescribed drill 
depth is reached. This provides the time 
base essential for all posttest 
analysis. 

Drill frequency. — For percussion 
drills, the number of blows per minute 
(BPM) can be used to determine if the 
drill is operating correctly and can also 
affect the noise frequency spectrum. 
Drill frequency information is supplied 
to the PC via an accelerometer mounted on 
the drilling rig and appropriate signal 
conditioning equipment. 



15 



Overall sound power . — The XT reads 
this value directly from the Bruel & 
Kjaer sound power calculator every 18 s, 
then resets the 7507 and the multiplexers 
for another sample. The PC is not in- 
volved in this process. The sound power 
levels displayed in figure 10 are linear 
(unweighted) values. Although A-weighted 
overall sound power levels would be more 
desirable from a perceptual standpoint, 
they cannot be obtained directly owing to 
the recording and calculating techniques 
used by the 7507.6 A-weighted levels can 
be obtained, however, through posttest 
analysis of the linear data. 

Although the XT serves primarily as a 
data collector during a normal test, the 
operator can also enter commands in mid- 
test through the XT keyboard. Most im- 
portantly, the operator can terminate a 
test at any time. It is also possible to 
change one or more of the control para- 
meters in fields 10 through 13 by typing 
new values in the appropriate field(s) 
and pressing the F9 key. The program 
responds with a message "New Parameters 
Sent" on the monitor, and the XT records 
the values and the time they were sent. 
This capability is especially advanta- 
geous because it minimizes the number of 
holes needed to establish the optimum set 
of operating parameters (i.e., the set 
that yields the maximum penetration rate) 
for a particular drill. 

A typical drill test requires approxi- 
mately 1,000 bytes of floppy disk space 
per foot of hole. Therefore, data from 
at least 30 tests (all 12-ft holes) can 
be contained on a single 360-kb floppy 
disk. Larger numbers of tests with shal- 
lower hole depths can also be retained on 
a single disk. Data collection and anal- 
ysis is discussed later in this report. 

6 The A-weighting process simulates the 
response of the human ear to sounds of 
various frequencies. The 7507 can record 
the desired 1 /3-octave band sound power 
levels only in the linear mode, so the 
subsequent calculation of the overall 
sound power level yields a linear value. 



Control Subsystems 

As described above, the ADTF consists 
of four major elements — the IBM-XT micro- 
computer, Westinghouse PC-700 process 
controller, Ledex valve drivers, and the 
various transducers and control valves on 
the drilling rig. This section describes 
how these elements function as a unit to 
provide the required control of the 
drilling process. 

IBM-XT Microcomputer 

The IBM-XT is a standard model with a 
360-kb floppy disk drive, a 10-Mb hard 
disk drive, a 256-kb random access memory 
(RAM), and a serial port for communica- 
tions with the PC-700. All the drill 
test software is permanently installed on 
the hard disk. Other add-on cards are 
installed for (1) a color monitor and 
graphics printer, (2) programming the PC- 
700, (3) interfacing with the Bruel & 
Kjaer sound measuring instrumentation, 
and (4) a real-time clock and calendar 
function. 

Westinghouse PC-700 Process Controller 

The PC-700 has a 4, 136-kb memory and 
can address 32 analog inputs, 32 analog 
outputs, 256 discrete inputs, and 256 
discrete outputs. The ADTF system uses 
14 analog inputs, 12 analog outputs, 4 
discrete inputs, and 16 discrete outputs. 
The drill operating information is passed 
to and from the PC via analog input 
cards, two analog output cards, one dis- 
crete input card, one discrete output 
card, and four high-speed counter cards. 
Four frequency-to-analog converter cards 
are also located in the PC-700 cabinet; 
although these are not addressed directly 
by the PC, they are essential for PC con- 
trol of flow-based processes. Power is 
supplied by three sources — a 5-V supply 
for the high-speed counters, a 15. 8-V 
supply for the input and output cards, 
and a 5-V supply for the frequency- 
to-analog converters. 



16 



All inputs such as transducer signals 
and control set points from the XT are 
converted to digital values and stored in 
selected memory cells called holding reg- 
isters. During operation, the PC 
achieves process control by comparing the 
actual values in the holding registers 
with those of their corresponding set 
points. Based on the difference between 
the actual and set point values, the PC 
program writes digital values to its out- 
put registers, which in turn activate the 
appropriate valves, valve drivers, or 
counters on the drill test rig. Also 
contained in the holding registers are 
values that control the rates at which 
the output registers are changed; this 
allows smoother operation of the drills 
and drilling rig. 

Drill Rig Positioning Control 

The control elements for carriage and 
boom movement are shown in figure 11. 
During initial startup, the PC moves the 
carriage and boom to the zero position, 
where the limit switches on the drilling 
rig are closed mechanically. Closure of 
the limit switches resets the PC's high- 
speed counters with actual values of zero 
and reference values corresponding to the 
set points previously entered into the 



XT. Based on the PC's comparison between 
the information provided by the position 
transducer (100 counts per inch input to 
the high-speed counter) and the count 
corresponding to the set point, the car- 
riage smoothly accelerates to its maximum 
speed, then decelerates as it approaches 
the set point position. After this posi- 
tion is reached, the PC nulls the Ledex 
driver card (input to Ledex of 4 V), thus 
closing the hydraulic control valve, and 
locks out the high-speed counter to make 
sure it does not change during the test. 
The above sequence is then repeated for 
the boom. After a test is completed and 
a new hole location is selected, the car- 
riage and boom move to the new position 
without moving to the zero position. 

Carriage Lock Control 

The carriage lock-unlock system, shown 
in figure 12, is somewhat simpler than 
the positioning system in that the PC is- 
sues only an on-off command to the hy- 
draulic control valve. The two horizon- 
tal locking cylinders in the carriage 
guide rail and the vertical foot jack 
(fig. 7) are connected in parallel to ex- 
tend and retract simultaneously. Prior 
to a carriage move, the PC sets the ap- 
propriate bits in the discrete output 



Position 
trans- 
ducer 



100 counts /in 



High-speed 
counter 



Limit switch 



or 24 V 



Digital 

signal out 

0-818 



Analog 

signal 0"24Vi 
out 
0-8 V 




Input from boom valve driver, p q Down 
similar to that of carriage 
valve driver 



X 



Up 



LI 



Carnage 

position 

motor 



Boom lift 
cylinder 



FIGURE 11.— Drill rig carriage and boom positioning system. 



17 



card to activate the "unlock" side of the 
hydraulic valve and deactivate the "lock" 
side. The reverse takes place after the 
carriage and boom have reached their set 
points, thereby locking the rig in place 
for the test. A timer loop in the PC 
program delays execution of further steps 



V off, 24 V unlock 



PC 



Bit set n 



a 



Discrete 

output 

card 



Hydraulic 

control 

valve 






V off, 24 V lock 



Locking 
cylinders 



\tp 



Foot jack 
cylinder 



ffi 



FIGURE 12. — Drill carriage lock system. 



until the locking or unlocking process is 
completed. 

Feed Thrust and Hole Depth Control 

The feed thrust and hole depth are con- 
trolled by the pressure and flow, respec- 
tively, of hydraulic oil in the feed cyl- 
inder. The upper portion of figure 13 
diagrams the feed thrust control, and the 
lower part describes the depth control. 

Since the area of the feed cylinder 
piston is fixed, the feed thrust is pro- 
portional to the hydraulic pressure on 
the larger (head) side of the piston. 
The pressure transducer in figure 13 
sends a voltage signal to an analog input 
card, which in turn assigns a digital 
value to a holding register in the PC. 
During drilling, the PC program compares 
this value to the set point and, depend- 
ing on whether the pressure needs to be 
increased or decreased, assigns an appro- 
priate digital value to an analog output 
card. The voltage at the output card is 
sent to the Ledex driver, which increases 
or decreases the current to the "Forward" 
side of the hydraulic control valve. 
This side of the valve then opens or 
closes to increase or decrease the pres- 
sure on the head side of the piston. The 
digital output of the PC is constrained 
within a relatively narrow range during 
the drilling mode to prevent the feed 



Pressure 
transducer 



Feed 
pressure 



^> 



Analog 
input card 

Volts (l~5 V) = pressure r-| Digital data 



Data input 



Total flow 
counts 



Flow- 
meter 



Feed 
flow 



Pulses = flow (38/in) 



dJ 



Limit 
switch 



High-speed 
counter 



Off (open), on (closed) 



(Feed retracted) 



Bit set 



Discrete 
input card 



Digital output 
413 = null n 



300 V= 
retract 




24 V 



-24 V f 



Forward 



0-8V 



4 V= null 



Analog 
output card 



Discrete 
output card 



Reset counter signal 



Valve 
driver 



; t „ 



X Hydraulic 
*-L valve 



? 



5 V = retract-^ 



Feed cylinder _Jo) 



Forward — ~ 
— Retract 



FIGURE 13.— Feed thrust and hole depth control system. 



18 



from lurching forward at the start of 
drilling, when the actual and set point 
pressures are far apart. A dead band 
around the set point is also included to 
prevent the feed pressure from oscillat- 
ing rapidly when the actual and set point 
pressures are very close but not 
identical. 

Hole depth is measured and controlled 
by the flow of hydraulic oil through a 
positive-displacement flowmeter in the 
line leading to the head side of the feed 
cylinder. This flowmeter generates 38 
voltage pulses per inch of feed travel, 
which are transmitted to the high-speed 
counter. The counter tallies the pulses 
and assigns the total count during a test 
to a PC holding register for comparison 
with the count corresponding to the drill 
depth set point. A normal test ends when 
the two counts are equal; at this point 
the XT commands the PC to stop drilling 
and retract the feed. 

To initiate the retraction phase, the 
PC sends a digital value of 300 to the 
analog output card, which then sends an 
input voltage of 3 V to the Ledex driver. 
The subsequent Ledex output is 5 V to the 
"Retract" side of the hydraulic control 
valve. This causes oil to flow to the 
rod side of the feed piston at a slow, 
constant rate to retract the drill. When 
the drill reaches the fully retracted 
position, the limit switch on the feed 
(fig. 6) closes mechanically. The PC 
then sends a null value (413) to the ana- 
log output card, thus stopping the feed, 
and sends a discrete output to the high- 
speed counter to zero the actual count 
for the next test. 



Pressure control for hydraulic hammers 
involves the same basic sequence as feed 
thrust control. Voltage from a pressure 
transducer is converted to a digital sig- 
nal and compared to the set point in the 
PC, which assigns an output that eventu- 
ally results in the opening or closing of 
a hydraulic valve. In the case of hammer 
pressure, only one side of the valve is 
activated because a reverse hammer func- 
tion is not required. As with feed pres- 
sure, the PC's digital output range is 
limited to prevent hammer pressure 
surges, and a dead band around the set 
point is included. 

Pressure control for pneumatic hammers 
includes the same type of analog input 
and PC comparisons as for hydraulic ham- 
mers, but the output involves three dis- 
crete control circuits. One circuit 
serves only to turn the main air supply 
valve on or off, as determined by the 
pneumatic-hydraulic choice entered into 
the XT (field 2 of figure 10). The other 
two circuits operate the pilot valve that 
controls the pressure-regulating valve 
(figure 14). After the PC compares the 
actual pressure to the set point, it 
opens one side of the pilot valve and 
closes the other. If the actual pres- 
sure is less than the set point, the PC 
opens the side that increases the pres- 
sure in the regulating valve. If the 
actual pressure is greater than the set 
point, the PC opens the opposite side of 
the pilot valve, reducing the pressure in 
the regulating valve. Reaction time of 
this system is very rapid and a dead band 
is included, so the amount of air vented 
to the atmosphere is minimal. 



Drill Hammer Control 



Drill Rod Rotation Control 



Two different types of drill hammer 
control systems are shown in figure 14; 
the top portion describes the analog con- 
trol system for hydraulic drills, and the 
lower part shows the discrete control 
system for pneumatic drills. The two 
systems are similar in that pressure is 
used as the process control variable, 
with flow being recorded in the PC for 
informational purposes only. However, 
the method for controlling pressure is 
somewhat different, as described below. 



Drill rod rotation control (fig. 15) is 
very similar to hammer control for pneu- 
matic and hydraulic drills, as can be 
seen by comparing figures 14 and 15. The 
major difference is that flow rather than 
pressure serves as the process control 
variable, with pressure being recorded 
for informational purposes only. Flow is 
the preferred control variable for rota- 
tion because the load on the rotation 
motor varies considerably during the 
course of a test (collaring, drilling, 



19 



Pressure Analog 

transducer Volts (l"5V) input card 
= pressure 



Hammer 
pressure 



O 



Hammer 
flow 



Control L^d data 
input values 



Frequency n 

= flow Data 

— I n input 



Flow 
transducer 



Digital 
data 



Volts (l"5V) = flow 



Frequency- 
to-analog 
converter card 



Digital output 
409-818 „ 



PC 



Analog 
output card 



HYDRAULIC DRILL SYSTEM 



0-24 V 



4-8 V 



Hydraulic 
drill 



Valve 
driver 



Hydraulic 

control 

valve 



Hammer 
pressure 



Pressure Ana|og 

transducer Vo | ts (|- 5V ) input card 

= pressure 



Control and data 
input values 



o 



Frequency 
= flow 



Hammer 
flow 



Data 
input 



Digital data 



PC 



Discrete 
output card 



On- off bit 
command 



V off, 24 V on 



V off, 

24 Von 

(decrease 

pressure) 



Volts (l"5V) = flow 



V off, 
24 V on 
(decrease 
pressure) 



Flow 
transducer 



Frequency- 
to-analog 
converter card 




PNEUMATIC DRILL SYSTEM 
FIGURE 14.— Drill hammer control system. 



Supply air 



Air supply 
valve 

Pneumatic 
drill 



Zl 



Pressure- 
regulating 
valve 



Pilot valve 



and retracting modes). Flow changes re- 
sulting from motor load changes are much 
smaller in magnitude than the associated 
pressure fluctuations, thus making a 
flow-based control system more 
desirable. 

Input signals are generated in the 
form of voltage pulses from turbine 
flowmeters, converted to analog signals 
by the frequency-to-analog cards, and 
sent to the PC via analog input cards. 
Output signals are generated by the PC 
based on the difference between the ac- 
tual flows and the set points. For hy- 
draulic rotation, the "Forward" side of 
the rotation valve is opened or closed 
proportionally via the Ledex driver to 
increase or decrease rotation flow. For 
pneumatic rotation, the pilot valve pres- 
sure regulating system described for 
pneumatic hammers is employed; in this 
case flow control is achieved through 
pressure changes. 



Another difference between the hammer 
and rotation control systems is that re- 
verse rotation is possible, although for- 
ward and reverse rotation cannot be 
achieved during the same drill test. Re- 
verse rotation can be obtained simply by 
reversing the hose connections to the 
rotation motor. 

Rotation flow is also monitored by the 
XT to serve as a safety shutdown during 
the drilling and retracting phases of a 
test. A rotation flow of zero indicates 
a stuck bit, which could cause damage to 
the bit, drill rod, and perhaps the drill 
itself. If the flow goes to zero during 
the drilling phase, the test is aborted 
and the retraction phase initiated. If 
the flow remains zero (unsuccessful re- 
traction), the PC goes into a null state 
to allow the stuck bit to be freed by 
hand. 



20 



Pressure Analog 

transducer Vo | ts (|- 5 v) j nput card 

= pressure 



Rotation 
pressure 



Data input 



C^ 



Rotation 
flow 



Frequency Control 
= flow ' and data 
input 



Digital data 



PC 



Digital output 
0-818 m 



0-24 V 



Flow 
transducer 



Volts (1-5 V) = flow 

Frequency- 
to-analog 
converter card 



0-8V 



Ana og 
output card 



HYDRAULIC DRILL SYSTEM 



Valve 
driver 



^Hydraulic 
O,cor 



? 



control 
valve 



0-24 V 




Hydraulic 

rotation 

motor 



Pressure Analog 

transducer Volts (l"5V) input card 
= pressure 



Rotation 
pressure 



Data input 



Frequency 

O^ ow 



Rotation 
flow 



Control 

and data 

input 



Digital data 



PC 



Discrete 
output card 



On -off 

bit 
command 



V off, 24 V on 

MAir supply 
V off, E 



Flow 
transducer 



Volts (1-5 V) = flow 
Frequency- 
to-analog 
converter card 



OVoff, 
24 Von 
(increase 
pressure) 



24 Von 

( decrease 

pressure) 



,nl 



F 



Supply air 

PNEUMATIC DRILL SYSTEM 
FIGURE 15.— Drill rod rotation control system. 



valve 



r 



5> 



1 



4 t 

u 



Pneumatic 

rotation 

motor 

Pressure- 
regulating 
valve 



-Pilot valve 



Flushing Water Control 

Flushing water is controlled by a sim- 
ple on-off command from the PC. When the 
test operator issues the final "Start 
Test" command through the XT keyboard 
(see "Data Input and Startup Procedure"), 
the PC activates a discrete output that 
opens the water valve completely. Water 
continues to flow to the drill until the 
feed limit switch is closed following 
drill retraction. Flushing water pres- 
sure is measured and recorded, but not 
controlled, by the PC and XT during the 
test. A manually operated pressure- 
reducing valve is used to adjust water 
pressure. 



Other Drill Test Commands 

The drill test program software permits 
several other operator command choices 
from the main test menu, as shown in the 
"Executive commands" box at the top of 
figure 10: 



results in 
level option 



Exit program (Fl) . — This 
the display of the higher 
menu of figure 9. 

Master reset (F2). — This nulls the PC 
holding registers that had previously 
contained set points or test data and 
changes the status word to that shown in 
figure 10. Resumption of testing after a 
"Master reset" command results in the 



21 



same sequence as the initial startup in 
that the drill carriage and boom move to 
the home position before moving out to 
the selected hole location. 

Move platform home (F3). — Moving the 
drilling rig to its home position places 
it close to the zero position, thereby 
shortening the initial startup process 
for the next test session. The home pos- 
ition is also the most convenient one for 
drill rig maintenance; therefore, this 
command is usually issued at the end of a 
drill test session or when a substantial 
amount of mechanical work (e.g. , changing 
drills) needs to be performed on the 
drilling rig. 

Test without move (F4). — This command 
starts the drilling process without mov- 
ing the carriage or boom. It is used 
most often when a successful move has 
been completed but the maximum hole depth 
has not been reached. For example, the 
operator may notice a problem (e.g. , 
stuck drill bit, leaking hose, etc.) and 
terminate the test before the hole is 
completed. The "Test without move" com- 
mand enables the test to be restarted 
(with a new test number) after the 



problem has been corrected without going 
through the time-consuming move process. 

HOLE LOCATION PROGRAM 

The hole location program is a very 
convenient means for managing the loca- 
tions and depths of all holes drilled by 
the ADTF. It can be accessed directly by 
the test operator to change the actual 
position of any row or column assignment 
in the hole location grid, or to change 
the depth (from the program's standpoint) 
of any hole on the existing grid. It is 
also addressed during the startup phase 
of the drill test program to prevent the 
use of a hole location that has already 
been drilled to the maximum depth of 
12 ft. These three functions of the hole 
location program are described below. 

Selection of Hole Position 

The test operator gains direct access 
to the hole location program by choosing 
option F3 in the menu of figure 9, which 
results in the display of figure 16, the 
hole location grid. The vertical hole 































ll In 


le 


ocation 


program | 


























































|HO 






























Fl 


Display 


location 








































F2 


Updat 


e 


ocation 


©-©L 


ocation 










Feed 1- 


(D Car 




© Boom 




















F6 


Print locati 


onj 






















Feed 2- 


© Car 




© Boom 






® Depth 








FIO 


Exit program 




1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


II 


12 


13 


14 


15 16 


17 


18 


19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 


A 































































































4 





B 





































































































C 





































































































D 





































































































E 




























































































6 


6 





F 





































































































G 











12 


3 


3 


2 
















































































H 





































































































1 



























































2 









































J 








2 








2 






































6 


2 


6 





5 





5 


























K 











1 


5 





4 


4 













































































L 





































































































M 





































































































N 











































































































































































































P 





































































































Q 





































































































R 






































































































Block 



Block 2 



FIGURE 16.— Data input menu for hole location program. 



22 



positions (hole rows) are denoted by the 
letters A through R; the horizontal posi- 
tions are given by columns 1 through 18 
(left-side concrete block) and 19 through 
36 (right-side block). Operator control 
of hole position is achieved by entering 
information in the circled fields 1 
through 6 in figure 16. Fields 1 and 2 
are the row and column assignments, re- 
spectively, of the hole to be considered. 
Fields 3 through 6 contain the desired 
number of counts (38 counts per inch) to 
be issued by the position transducers en 
route from the home position to the hole. 
Fields 3 and 4 are the carriage and boom 
counts for feed 1, while fields 5 and 6 
are for feed 2. These data are then 
placed into the appropriate PC holding 
registers by pressing the "Update loca- 
tion" (F2) key. A current listing of the 
counts for each hole location can be ob- 
tained by pressing either Fl (output to 
video monitor) or F6 (output to printer). 
The entire hole location grid was pre- 
programmed in this manner to remain with- 
in the confines of the two existing con- 
crete blocks. Spacing between adjacent 
rows and columns was set at 4 in, and the 
pattern was staggered by 2 in (i.e., 
even-numbered columns were shifted 2 in 
downward from odd-numbered columns) to 
provide an actual hole spacing of about 
4.5 in. Under normal circumstances, the 
test operator would have no reason to 
change the preprogrammed hole positions. 
However, an important exception occurs 
when considering the use of drilling 
media other than the concrete blocks. 
For example, a granite test block was in- 
serted into the wall between the concrete 
blocks, and previously unused hole loca- 
tions around the perimeter of the con- 
crete blocks were utilized to establish a 
hole pattern on the granite block. The 
only constraints on hole position are the 
physical travel limits of the carriage 
and boom. 

Validation of Input Data 

At the end of each drill test, the 
drill test program automatically enters 
the hole depth (in feet) into the 
hole location program. If the operator 



subsequently specifies a hole location 
that has already been drilled to the max- 
imum depth (e.g. , location G-5 in figure 
16) or asks for a depth that would exceed 
the maximum at that location (e.g., a 7- 
ft hole at location J-21), the drill test 
program issues an error message. Testing 
cannot proceed until the error is cor- 
rected by specifying either another hole 
location or a shallower hole depth. 

Selection of Hole Depth 

During the initial programming of the 
hole location grid, the depth of each 
hole was set to zero via field 7 of fig- 
ure 16. Subsequent drill tests resulted 
in the assignment of actual hole depths 
to various locations. In some cases, 
however, it is desirable for the operator 
to arbitrarily assign hole depths through 
the hole location program. For example, 
a very large drill hole at a particular 
location may interfere with adjacent 
holes if the holes are not perfectly 
straight; damage to the drill rod or 
drill could result if the holes intersect 
within the block. Therefore, even though 
the actual depths of the adjacent holes 
are zero, the operator may wish to enter 
a depth of 12 ft into the hole location 
program (field 7 of figure 16). This 
will cause an error message to appear if 
the operator tries to select these holes 
for drill tests. The hole depth selec- 
tion feature also allows easy re- 
initialization after the concrete blocks 
are replaced. 

DATA ANALYSIS PROGRAM 

The drill test software possesses very 
powerful analytical capabilities. Any 
drilling parameter stored to disk can be 
studied and compared graphically to any 
other variable. The data analysis pro- 
gram can be called in from the overall 
software menu (fig. 9) or the main drill 
test menu (fig. 10) for simultaneous 
analysis of any two tests. The data re- 
corded to disk can also be converted 
easily to commercially available spread- 
sheet files (Lotus 1-2-3) for subsequent 
analysis using the spreadsheet software. 



23 



Direct Data Analysis and Graphics 

Test Selection 

Recall that all test data are stored on 

floppy disks in files namea "TEST .- 

DAT," with the blanks corresponding to 
the four-digit test number assigned by 
the XT. When data analysis is desired, 
the test operator first makes sure the 
correct test numbers are available on the 
floppy disk by selecting option F4, "Di- 
rectory of tests on A:" from the overall 
software menu shown in figure 9. The 
operator then chooses the data analysis 
program (F2), which results in the dis- 
play of the menu in figure 17. The test 
or tests to be analyzed are selected by 
entering the four-digit test number(s) 
in fields 1 and 2 of figure 17 and press- 
ing the F9 "Retrieve tests (s)" key. Note 
in figure 17 that tests 0178 and 0293 
have been selected. Test 0178 is that of 
a small, muffled pneumatic percussion 
drill; test 0293 is that of a small, all- 
rotary pneumatic drill. These two tests 
will be used below to illustrate the 
basic graphics capability of the data 
analysis program. Further comparisons 
between the two drills are contained in 
the section of this report entitled "Ini- 
tial Test Results." 



Raw Data Retrieval 

The "List test" and "Print test" op- 
tions in figure 17 (function keys F7 and 
F8) are used to retrieve all the data re- 
corded during a given test. "List test" 
displays the data only on the XT video 
monitor; "Print test" also provides a 
hard copy of this information. Figure 18 
shows the data recorded for the first 45 
s of test 0293. Descriptive information 
is given at the beginning of the test 
file, and the entry of new test parameter 
values is documented at 15.7 and 26.3 s. 
The top row of figure 18 shows all the 
drilling parameters recorded during the 
test and the units in which they are 
given. Sound power information is given 
at 18.1 and 36.2 s; the first 21 values 
in the string correspond to the twenty- 
one 1/3-octave bands comprising the 100- 
to 10,000-Hz frequency range, and the 
final value is the overall (unweighted) 
sound power level. Note that in this 
particular test, the values for hammer 
pressure and drill blow frequency appear 
as dummy values of 1.0 and 0.0, respec- 
tively, because of the all-rotary operat- 
ing mode of the tested drill. 

The ability to scan the entire set of 
test data in this manner helps the test 
operator in several ways: (1) Graphs 







menu 




Fl 


Analysis 


Plot feed thrust 


Plot hammer pressure 


F2 


F3 


Plot feed rate 


F4 


Plot sound power 


F5 


Plot spectrum 


F6 


Plot spectrum waterfall 


F7 


List test 


F8 


Print test 


F9 


©Retrieve test: 0178 
©Retrieve test: 0293 


FIO 


Exit 



©X minimum ®X maximum 
©Y minimum ®Y maximum 



FIGURE 17. — Data input menu for analysis program. 



24 



Test 0293 

Drill tested' GOPHER Pneumatic or hydraulic: P Feed" I Hole size : \V\e" 

Drill steel- 1" HEX Bit type- POS R Location: I -02 

Comments : retest GOPHER at optimum settings 



Time, 
s 


Rotation 
flow, 
g/cf' 


Distance 

drilled, 

in 


Hammer 
pressure, 
psi 


Feed 
thrust, 

Ibf ' 


Feed 
rate, 
in/s 


Drill 
frequency, 


Hammer 


Rotation 
pressure, 
psi 


Flushing 
water, 
psi 




Values- Hammer pressure = 1 Rotation flow = 100 
Feed thrust = 200 Distance drilled = 48 


0.1 


102.1 


0.1 


1 


201.6 











90.4 


52.5 


4.1 


102.3 


4.5 


1 


204.1 


I.I 








82.1 


60 


8.1 


101.8 


6 


1 


199 


0.4 








83.6 


61 


12.1 


85.4 


6.3 


1 


209.3 


0.1 








76.7 


60 


15.7 


New Hammer pressure = 1 Rotation flow = 120 
values : Feed thrust = 200 Distance drilled = 48 


16.1 


86.2 


6.5 


1 


188.6 


0.1 








78.7 


60.1 


18.1 


Sound power, 81.2, 83.4, 85.4, 87.7, 92.5, 92.1, 97, 93.5, 91.6, 96.8, 
d B= 93.8, 97.5, 94.9, 88.9, 973, 92.3, 91.2, 88.9, 85.9, 
86.2, 105.4 


20.2 


116.9 


6.7 


1 


201.6 


0.1 








100.2 


60.4 


24.2 


117.2 


7 


1 


201.6 


0.1 








97.8 


60.7 


26.3 


New Hammer pressure = 1 Rotation flow = 120 
values^ Feed thrust = 500 Distance drilled = 48 


28.2 


112.6 


8.1 


1 


739 


0.3 








97.3 


61 


32.3 


113.9 


9.7 


1 


522 


0.4 








101.7 


60.7 


36.2 


Sound power, 83, 85.6, 87, 89.7, 95, 95.5, 99.3, 95.7, 93.5, 
dB= 100.6, 97.5, 98.6, 99.2, 93.2, 96.1, 94.7, 93.8, 
92.4, 90,90.2, 90.9, 1078 


36.5 


112.3 


11.3 


1 


532.3 


0.4 








99.7 


60.6 


40.6 


II 2.1 


12.5 


0.5 


558.1 


0.3 








97.8 


60.9 


44.7 


114.4 


13.8 


1 


480.6 


0.3 








99.2 


60.6 



Note : the notation g/cf for rotation flow reflects 

fact that flow is measured in gpm for hydraulic 
drills and cfm for pneumatic drills. 



FIGURE 18— Printout of drill test data. 



25 



generated by the software are more easily 
interpreted with the availability of hard 
numbers, especially when input parameters 
are changed during a test, (2) particu- 
larly interesting portions of a test can 
be isolated for more detailed analysis, 
and (3) data anomalies that sometimes oc- 
cur at the start of a test are easier to 
identify. 

Basic System Graphics 

The function keys Fl through F6 in fig- 
ure 17 are used to display graphs on the 
XT video monitor; hard copies are ob- 
tained easily by pressing the "Print 
screen" key of the XT keyboard when the 
graph is displayed. Function keys Fl 
through F4 provide graphs that utilize 
the indicated test parameter as the de- 
pendent (Y-axis) variable and elapsed 
time as the independent (X-axis) 



variable. Function key F5 plots the 1/3- 
octave band sound power levels versus 
frequency, and F6 provides a simulated 
three-dimensional graph with frequency as 
the X-axis, 1/3-octave band sound power 
level as the Y-axis, and time as the Z- 
axis. Figures 19 and 20 are examples of 
these graphs for tests 0178 and 0293. 

Fields 3 through 6 in figure 17 are 
used by the test operator to define the 
range of values to be displayed on the X- 
and Y-axes of each graph. These values 
are entered before pressing the function 
key for the desired graph. If these 
fields are left blank, the range is de- 
termined by the actual minimum and maxi- 
mum values contained in the data. In 
figures 19 and 20, ranges were selected 
such that all test data would be dis- 
played on easily readable axes. For 
example, the total elapsed time in each 
test was slightly greater than 150 s; 



(A 
Q. 

Ill 

QC 

Z> 

<n 
en 

UJ 

rr 
o. 

a: 



< 

x 



UJ 

a 

UJ 
UJ 



75 




1 1 

^-Test 0178 


50 


I 


- 


25 


■— 1 


r-Test 0293 



800 




200 




200 



CO 

"o I20h 



UJ 

r?. 115 



8 M0 

o 

°- 105 

a 

z 

o ioo 

CO 



95 






Test 0178 




Test 0293 



50 100 150 200 50 100 

TIME, s 
FIGURE 19.— Graphs of hammer pressure, feed thrust, feed rate, and sound power versus elapsed time. 



1 50 



26 





110 




105 




100 




95 


m 


90 


_i 

UI 


85 


> 




U 




_l 


80 


E 




UJ 


110 


o 




0. 






105 


Q 




Z 




3 
O 


100 


</) 






95 




90 




85 




80 



1 




1 ' 


. 




r Test 0178 


"I 1 T— ' 1 1 1 1— 

\s 
\ \ 


f\ "N. 


/vs J> — : 

/ \ /A rTest 0293 
/^ ^ V/ \ 1 


! 




■ i 




I 6 II 16 21 

FREQUENCY, l/3"octave band number 

FIGURE 20.— Sound power spectrum and spectrum waterfall 
graphs. 

therefore, the "Xmax" (field 4) value in 
the time-based graphs was set at 200 s so 
that values of 50, 100, and 150 s would 
occur at the three computer-generated 
subdivisions. Maximum and minimum values 
for all the other parameters were chosen 
in the same manner. 

Hammer pressure (fig* 19). — Ha mme r 
pressure for test 0178 (pneumatic percus- 
sion drill) was set at 90 psi; the ADTF 
achieved this pressure shortly after 
startup and maintained it very con- 
sistently throughout the test. Hammer 
pressure for test 0273 was set at a nom- 
inal value of 1 psi (rotary drill). 

Feed thrust (fig. 19). — Feed thrust in 
test 0178 was set at 240 lbf and remained 
there throughout the test. Feed thrust 
in test 0293 was initially set at 
200 lbf; after the hole was collared, 
thrust was increased to 500 lbf. Except 
for the brief spike that occurred as the 
ADTF adjusted to the higher set point, 
feed thrusts remained fairly close to the 
set point values. 

Feed rate (fig. 19). — The abnormally 
high feed rate at the start of each test 
corresponds to the forward movement of 
the drill before the bit contacts the 
concrete. After collaring, both drills 



achieved a fairly steady feed rate of 0.3 
to 0.5 in/s, although the percussion 
drill was somewhat faster. In test 0293, 
an abnormally low feed rate occurred dur- 
ing collaring because of the low feed 
thrust; this rose markedly when the feed 
thrust was increased. 

Sound power (fig. 19). — Sound power of 
the rotary drill (test 0293) was very 
consistent at 105 to 107 dB through the 
test. Sound power of the percussion 
drill (test 0178) was around 115 dB at 
the start of the test, but decreased as 
the drill rod entered the hole. This ef- 
fect did not occur in test 0293 because 
the drill rod is not a major contributor 
to rotary drill noise. 

Spectrum (fig. 20). — The 1/3-octave 
band sound power levels in these two 
tests were very similar at low frequen- 
cies. The major difference between the 
two spectra occurred at higher frequen- 
cies, where the drill rod noise of the 
percussion drill was more prominent. 

Note in figure 20 that frequency data 
are reported in "band number" rather than 
Hertz because this is the way the sound 
power calculator reports frequency data 
to the XT. In this case, band 1 corre- 
sponds to 100 Hz and band 21 corresponds 
to 10,000 Hz. However, since Hertz is 
the universally accepted unit of fre- 
quency measurement, the use of band num- 
ber in graphs represents a major defi- 
ciency of the basic system graphics. Two 
other limitations of the basic system 
graphics for sound power spectra are that 
(1) only the final sample recorded during 
the test is graphed when the F5 key in 
figure 17 is pressed and (2) the overall 
sound power level cannot be plotted on 
the same graph as the 1/3-octave band 
data. As discussed in the next section, 
all three of these problems can be re- 
solved by using electronic spreadsheets 
to look at frequency data. 

Spectrum waterfall (fig. 20). — Th i s 
shows how the noise frequency spectrum 
varies during a test. It can provide 
useful qualitative information with re- 
gard to frequency shifts during the 
course of the test, but it is of little 
value for quantitative comparisons. Ow- 
ing to the complexity of the spectrum 



27 



waterfall graph, it can be displayed for 
only one test at a time. 

Expanded Data Analysis Through 
Spreadsheets 

Given the limitations of the basic sys- 
tem graphics, a method for obtaining a 
more complete data analysis was desired. 
The most effective approach was to con- 
vert the test data files to electronic 
spreadsheet files. Lotus 1-2-3 was 
chosen as the spreadsheet program because 
of its ready availability and compatibil- 
ity with the IBM-XT. To avoid the manual 
entry of test data into the spreadsheet 
files, special software was written to 
convert the individual parameters of the 

"TEST .DAT" files into a format that 

could be read by the lotus program's 



"File Import" function. For convenience, 
the Lotus Formatter program and the stan- 
dard Lotus 1-2-3 software are contained 
on the hard disk. 

File Conversion Procedure 

The step-by-step procedure for convert- 
ing the "TEST .DAT" files to Lotus 1- 

2-3 files is described below: 

1. The test operator loads the Lotus 
Spreadsheet Formatter program into the 
XT, which results in the display of the 
menu shown in figure 21. 

2. The four-digit test number of the 
test to be formatted is entered into 
field 1 of figure 21. 

3. The parameters to be formatted 
are selected by placing any nonzero 















opreaasheei rurmauer 




F 1 Exit 






F5 Delete specific ??x. PRN files 


F9 Extract drill test data FIO Extract noise test data 






Test (T> » 


© HPx. PRN 
© HFx. PRN 


Hammer pressure Drill test only 
Hammer flow 








© RPx. PRN 


Rotation pressure 




© RFx. PRN 


Rotation flow 




© FTx. PRN 


Feed thrust 




® FRx. PRN 


Feed rate 




© DFx. PRN 


Drill frequency 




® DDx. PRN 


Distance drilled 




© FWx. PRN 


Flushing water 




© SPx. PRN 


Sound power 




@ ASx. PRN 


Average spectrum 




@ PSx. PRN 


2131 Average spectrum 


® Target director 


y : 


© x = 1 


© Resample time : 1 s © Start time 5 s ® Stop time : 60 s 



FIGURE 21. — Data input menu for Spreadsheet Formatter program. 



28 



character in fields 2 through 13. The 
general names of the files to be created 
by the Lotus Formatter (see item 5 below 
for specific file names) are shown im- 
mediately to the right of fields 2 
through 13, and the parameter names are 
displayed on the right of the file 
names. 

4. The disk drive to which the format- 
ted files will be written is entered into 
field 14. The hard disk (c): is the 
default drive. 

5. The specific names of the files to 
be created by the Lotus Formatter are 
chosen by entering any of the numbers 1 
through 9 into field 15. For example, if 
nonzero characters were entered in fields 
2 and 9 and the default value of 1 were 
left in field 15, the two files created 
would have the names "HP1.PRN" and 
"DDI.PRN." Up to nine Lotus-formatted 
files for each parameter can thus be con- 
tained on any one output target (floppy 
or hard disk), and almost an unlimited 
number of such files can be maintained 
by renaming the files after they are 
formatted. 

6. The amount of drill test data to 
be formatted is chosen by entering the 
appropriate values in fields 16, 17, and 
18. Since the Lotus Formatter program 
uses the "Elapsed Time" parameter as a 
key, field 17 (Start time) and field 18 
(Stop time) determine the portion of the 
test to be formatted. The default values 
of 0.0 and 60.0 s are shown in figure 21. 
Field 16 (Resample time), specifies the 
interval at which the Lotus Formatter 

program will recheck the "TEST .DAT" 

file for new data. When the default val- 
ue of 1.0 s is shown in figure 21, the 
program interpolates between the actual 
values recorded at 4- or 18-s intervals. 

7. When all selections in fields 1 
through 17 have been made, the F9 key is 
pressed to perform the file conversions. 
Confirmation messages and/or error mes- 
sages appear at this time, including an 
option to overwrite any "xxx. PRN" files 
that are already located on the target 
directory. Pressing F5 rather than F9 
deletes from the target directory any 
files whose names are the same as those 
of the "marked" files. 



8. The operator exits the Lotus For- 
matter program, enters Lotus 1-2-3, and 
calls in a special worksheet file that 
contains A-weighting correction factors, 
convenient column headings, and appropri- 
ate axis labels for later graphs. This 
serves as a template worksheet to which 
the formatted drill test files will be 
imported. 

9. The cursor is moved to the area of 
the worksheet in which the test data are 
to appear, and the "File Import" proce- 
dure of Lotus 1-2-3 is used to call in 
the formatted files. This procedure is 
repeated for each "xxx. PRN" file created 
in steps 1 through 7 above. 

10. The standard Lotus 1-2-3 file man- 
ipulation and graphics options are uti- 
lized to perform the desired analyses. 
Examples of the use of Lotus graphics are 
given in the section of this report 
entitled "Initial Test Results." 

Note that fields 2 through 11 corres- 
pond to the drilling parameters listed in 
figure 18. Fields 12 and 13 are special 
parameters that are created by the Lotus 
Formatter software prior to conversion. 
The "Average spectrum" (field 12) con- 
sists of the logarithmic average of the 
sound power levels in each of the twenty- 
one 1/3-octave bands, with the number of 
samples determined by the specified start 
and stop times. For example, the default 
values of 0. and 60. s would result in 
the averaging of three sound power values 
per frequency band (data at 18, 36, and 
54 s). Field 13 is analagous to field 12 
except that the Lotus Formatter looks for 
sound pressure data recorded from the 
Bruel & Kjaer model 2131 digital fre- 
quency analyzer. 

Advantages of Spreadsheet Analysis 

Multivariable Comparisons 

The basic system graphics package can 
only plot drilling parameters versus 
time. With spreadsheet analysis, any two 
parameters in a given test can be com- 
pared against each other. The most fre- 
quent use of this capability would be the 
comparison of sound power and hole depth. 



29 



Also, if one or more drilling parameters 
are changed during the test, the effect 
of these changes on all other parameters 
can be displayed graphically. 

Multitest Comparisons 

The Lotus 1-2-3 graphics package can 
display the results of up to six tests on 
the same graph, versus only two for the 
basic system graphics package. Para- 
metric studies (where only one variable 
is changed from test to test, to observe 
its effect on other variables) are there- 
fore much easier to perform. This cap- 
ability also facilitates comparisons 
among several different types and models 
of drills. 

Frequency Analysis 

As mentioned above, the limited fre- 
quency analysis capability of the basic 
system graphics package is one of its 
greatest deficiencies. Spreadsheet anal- 
ysis overcomes these deficiencies in the 
following ways: 

1. The average frequency spectrum from 
any portion of the test can be obtained 
by judicious selection of the start and 
stop times in the Lotus Formatter program 
(fields 17 and 18 in figure 21). In this 
manner a two-dimensional "spectrum water- 
fall" can be created to observe how the 
spectra change during the course of a 
test. 



2. A-weighting of the 1/3-octave band 
noise levels can be performed quickly and 
easily. An overall A-weighted level for 
each spectrum can then be calculated and 
displayed on the same graph as the 1/3- 
octave band data. 

3. Frequency rather than band number 
can be displayed as the X-axis of all 
graphs. 

Analysis of Other Noise Tests 

Since the Lotus Formatter can operate 
on any data file created by the sound 
measuring instrumentation, it can be used 
to analyze noise information from any 
test conducted in the reverberation cham- 
ber. A separate noise test program al- 
lows this instrumentation to be activated 
through the XT, and causes it to write 
the noise data to disk with a file name 
of "NOIS .DAT". The Lotus Formatter 
program can then be used to convert the 
data to a "xxx.PRN" file. The same 10- 
step procedure described above is used 
instead of the F9 "Extract drill test 
data" command. As noted in figure 21, 
drilling parameters cannot be converted 
using the F10 command. One of the most 
common uses of the noise test program is 
to read the room correction factors from 
the Bruel & Kjaer 7507 sound power cal- 
culator. Knowledge of these room correc- 
tion factors allows the sound pressure 
levels to be calculated from the sound 
power levels using the Lotus software. 



INITIAL TEST RESULTS 



To further demonstrate the abilities of 
the automated drill test fixture, some 
observations of the initial test data are 
included. Three types of drills were 
tested to help assure that the test fix- 
ture was capable of performing as speci- 
fied. A pneumatic percussion drill, a 
hydraulic percussion drill, and a pneu- 
matic rotary drill were all run in the 
concrete test medium to compare perfor- 
mance against the manufacturers ' pub- 
lished data and to measure their sound 
power levels in an operating situation. 
All three drills are of the small 



"hand-held" class for which noise control 
technology has been difficult to 
implement. 

The general test scheme involves find- 
ing the set of operating parameters that 
results in the optimum penetration rate 
for the drill being tested and measuring 
the sound power level under these condi- 
tions. However, drills designed to oper- 
ate in soft rock perform better in the 
concrete test medium than those designed 
to drill hard rock. Therefore, it is 
possible that the penetration rates pre- 
sented here could be different if the 



30 



drills were tested in a hard drilling 
medium. 

Several points should be noted about 
the test data. Most importantly, the 
number of tests to date is too small to 
generate statistically valid results con- 
cerning the behavior of the drills under 
differing operating conditions. Second, 
the primary purpose of these tests has 
simply been to verify the capabilities of 
the ADTF in terms of process control, 
data collection, and test analysis; how- 
ever, operation of the test fixture has 
still yielded some interesting informa- 
tion. The confirmation of the contribu- 
tion of the drill steel to the overall 
noise level in percussion drills is one 
factor that can be noted from the avail- 
able data. 

PNEUMATIC VERSUS HYDRAULIC PERCUSSION 
DRILLS 

The drill used for the tests of pneu- 
matic percussion drill was a Technologi- 
cal Enterprises QHR drill, a quieted 



pneumatic drill developed under contract 
with the Bureau of Mines (9-10). Its 
valveless design, independent rotation, 
and integral muffler make the QHR drill 
one of the quietest in its class. A Tarn- 
rock HH-50 was chosen to represent hy- 
draulically powered percussion drills. 
This drill also has independent rotation 
and is capable of accommodating either 
water or air flushing, as is the QHR. 
The sound power spectra of these two 
drills are shown together in figure 22. 

The QHR and the HH-50 are in approxi- 
mately the same weight and power-output 
class and give a fairly good comparison 
between the two different power sources. 
During the tests chosen for comparison, 
the QHR drilled at a rate of 1.95 ft/min 
under an average thrust of 245 lbf and 
the HH-50 drilled at a rate of 
2.20 ft/min under an average thrust of 
277 lbf. Although they are not typically 
used for concrete drilling, button bits 
were used to maintain bit consistency 
during testing. 



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■ Pneumatic percussion drill 
a Hydraulic percussion drill - 



25 



250 



500 1,000 2,000 4,000 8,000 16,000 
FREQUENCY, Hz 

FIGURE 22. — Average frequency spectra: pneumatic and hydraulic percussion drills. 



31 



It can be noted in figure 22 that the 
drills differ significantly in sound 
power output between 160 and 1,250 Hz. 
This area is dominated by the noise pro- 
duced by the exhaust of the pneumatic 
drill. The difference would be even 
larger if the pneumatic drill were not 
muffled. At 1,000 Hz and above, the two 
drills produce approximately the same 
power spectrum. This is to be expected 
as the noise in this frequency range is 
characteristic of the drill body and 
drill steel. 

The sound power output at 1,250 to 
8,000 Hz is largely a product of the ex- 
posed drill steel. In particular, the 
spectra from 1,250 to 4,000 Hz are almost 
identical. This is not surprising be- 
cause the two drills operate at about the 
same frequency and the length of the 
steel in both tests was the same. This 
noise is not produced solely by the drill 
itself, and in operating situations it is 
inseparable from the drill body noise. 

In the future, when tests for actual 
drill sound power output are performed, 
the drill steel noise will be eliminated 
by removing the steel from the test. 
This will be accomplished by using a 
"dead block." The dead block is simply a 
device that can absorb and dissipate the 
energy produced by the drill, usually in 
the form of heat. The drill will be 
coupled to the dead block by a very short 
section of steel that will be acoustical- 
ly isolated from the test environment. 
For the present, however, the dead block 
is not being used so the effect of the 
drill steel can be observed as it occurs 
in the actual operation of the drill. 

Research by Hawkes (12) shows that 
noise produced by the drill steel is 
caused primarily by bending waves in the 
steel. These bending waves occur at many 
frequencies above a critical frequency 
and are calculated by the formula 



where fe = bending wave frequency, Hz, 



n - 

D = 
L = 

and C, = 



mode number (1 for first 
critical frequency), 

drill steel diameter, in, 

drill steel length, in, 

speed of sound in drill 
steel, 2 x 10 5 in/s. 



f R = n 2 



DC, 



[l-1.2(nD/L)2], 



TIT 



These bending wave frequencies are 
spaced sufficiently close together to 
produce noise in all 1/3-octave bands 
above the initial frequency. 

Note in the above equation that the 
bending wave frequencies are directly re- 
lated to the length of the drill steel; 
the longer the steel, the lower the first 
critical frequency. The drill steel 
used in the tests of the percussion 
drills was 10 ft in length, resulting in 
a first critical frequency of approxi- 
mately 5 Hz, well below the 1/3-octave 
band centered at 31.5 Hz. The contribu- 
tion to the overall noise level occurs in 
all bands measured but is considerably 
larger at frequencies above 2,000 Hz 
(fig. 23). This is of particular import- 
ance up to 4,000 Hz because of the poten- 
tial effects on hearing loss. The noise 
levels drop over the course of a test due 
to the entrance of the drill steel into 
the hole. The section of steel that has 
penetrated is shielded from the test en- 
vironment, and the overall contributution 
of the steel is thus reduced. 

This type of information is particular- 
ly useful when designing noise controls 
for drills or when attempting to develop 
noise-controlled operating procedures. 
The time effects would be difficult to 
observe with traditional data collection 
methods but are easily noted by the reg- 
ularly spaced intervals of data provided 
by the test fixture's data collection 
system. 



32 



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Pneumatic percussion dri 




125 250 500 1,000 2,000 4,000 8,000 16,000 




250 500 1,000 2,000 4,000 8,000 16,000 
FREQUENCY, Hz 

FIGURE 23. — Frequency spectra for percussion drills, begin- 
ning versus end of hole. 



ROTARY VERSUS PERCUSSION DRILLS 

A pneumatic rotary drill, the ALMINC0 
Gopher, was also tested on the drill test 
fixture. The intended uses of the Gopher 
are roughly the same as for the two per- 
cussion drills; however, rotary drills 
operate at higher thrust levels than per- 
cussion drills. This fact, combined with 
the different control demands of a rotary 
drill, allowed the test fixture to be 
operated over a greater range of thrust 
values than when testing percussion 
drills alone. The Gopher drilled at a 
rate of 1.57 ft/min under an average 
thrust of 521 lbf during the test se- 
lected for comparison. The data re- 
trieved from the tests of the rotary 
drill provide some interesting contrasts 
to both of the percussion drills. 

The sound power spectrum of the rotary 
drill is similar to that of the pneumatic 
percussion drill from the standpoint of 
the pneumatic exhaust, but it differs 
from those of the percussion drills in 



the relatively minor contribution of 
drill steel noise. These observations 
are evident in figure 24. The portion of 
the spectrum from 200 Hz to 1 kHz is 
greater in level for the two pneumatical- 
ly powered drills than for the hydrau- 
lically powered drill. The greater con- 
tribution by the drill steel of the per- 
cussion drills can be seen at 2 kHz and 
above. The absence of drill steel noise 
is also shown in the sound power levels 
taken at intervals during the test. 
The overall levels for the rotary drill 
differ by less than 1 dB from beginning 
to end, and the average spectra are ap- 
proximately the same (fig. 25), indicat- 
ing that noise radiated from the rotary 
steel is not a major contributor to the 
overall noise level. 

Another good example of the types of 
phenomena that can be observed is illus- 
trated by the shape of the average test 
spectra (fig. 24). A potential problem 
with the rotary drill is revealed near 
the center of the graph. It can be noted 
from the graph that the portion of the 
spectrum from which a majority of the 
noise is produced is in a relatively 
small range that differs from the predom- 
inant noise of the percussion drills. 
The span of frequencies in the 1/3-octave 
bands centered from 800 to 1,600 Hz con- 
tains over half of the total sound 
energy. These frequencies overlap the 
range of human speech. Hearing loss at 
these frequencies greatly impacts func- 
tional hearing ability. Based on the ob- 
servation of overall levels alone, or 
even individual narrow band spectra pro- 
duced from recordings of field test, one 
may conclude that the rotary drill is 
less of a noise problem than the percus- 
sion drills; however, by examining the 
operation of the drill more closely, it 
can be seen that a more thorough investi- 
gation of the sources is necessary. 

The positive side to this particular 
observation is that the peak noise pro- 
duced by the rotary drill has more poten- 
tial solutions than the noise produced by 
the percussion drills. The frequency 
range of the noise, along with informa- 
tion about the operating principles of 
the drill, suggests that the noise arises 
from the gear motor that drives the 



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■ Pneumatic percussion drill 
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• Pneumatic rotary drill 



125 250 500 1,000 2,000 4,000 8,000 16,000 

FREQUENCY, Hz 

FIGURE 24.— Average frequency spectra: pneumatic and hydraulic percussion drills, pneumatic rotary drill. 



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FREQUENCY, Hz 

FIGURE 25.— Frequency spectra for pneumatic rotary drill: beginning versus end. 



34 



drill. This type of noise can sometimes 
be attenuated by redesigning the rotors 
and reduction gears to shift the fre- 
quency into a more tolerable range. 

It should be pointed out again that 
these are merely observations of selected 



test data and are in no way statistically 
representative of the way the drills 
behave, especially in terms of penetra- 
tion rate. 



DISCUSSION 



The automated drill test fixture is a 
very powerful tool for studying the noise 
characteristics and operational perfor- 
mance of percussion and rotary drills. 
The unique feature of the ADTF is that it 
is housed within a large reverberation 
chamber to allow the easy calculation of 
drill sound power levels. Sound power 
data are not usually provided by drill 
manufacturers, so the ADTF can supply 
drill users with information that has 
previously been unavailable. If noise is 
a consideration when selecting a drilling 
system, this information can be very 
valuable. 

The ability to achieve control over all 
important drill operating parameters is a 
key advantage of the ADTF. Test condi- 
tions can thus be reproduced exactly or 
changed to study the effect of one or 
more parameters on the overall perfor- 
mance of the drill. Diagnostic work of 



this type can provide useful information 
on drill penetration rate as well as 
noise. The ability to change drilling 
media is very important when examining 
drill penetration rate. Each drill must 
be tested in the medium for which it was 
designed (soft, medium, or hard rock) in 
order to make valid comparisons of drill 
penetration. 

Initial tests conducted with the ADTF 
confirmed that it is capable of achiev- 
ing the desired process control and data 
recording functions. The data analysis 
software greatly facilitated the inter- 
pretation of these initial tests. Gen- 
eral observations were made with respect 
to the noise produced by pneumatic per- 
cussion, hydraulic percussion, and pneu- 
matic rotary drills. A much more exten- 
sive testing program with each of these 
drills must be conducted before defini- 
tive comparisons can be made. 



REFERENCES 



1. Patterson, W. N. , G. G. Huggins, 
and A. G. Galaitsis. Noise of Diesel- 
Powered Underground Mining Equipment: 
Impact, Prediction, and Control (contract 
H0346046, Bolt Beranek and Newman, Inc. ). 
BuMines OFR 58-75, 1975, 227 pp.; NTIS 
PB 243 896. 

2. Visnapuu, A. , and J. W. Jensen. 
Noise Reduction of a Pneumatic Rock 
Drill. BuMines RI 8082, 1975, 23 pp. 

3. Summers, C. R. , and J. N. Murphy. 
Noise Abatement of Pneumatic Rock Drill. 
BuMines RI 7998, 1974, 45 pp. 

4. George, D. L. , and N. J. Matteo. 
Development of Noise Control Technology 
for Pneumatic Jumbo Drills (contract 
HO395029, Ingersoll-Rand Research, Inc. ). 
BuMines OFR 100-81, 1980, 61 pp. ; NTIS 
PB 81-237414. 

5. Dixon, N. R. , and M. N. Rubin. 
Development of a Prototype Retrofit Noise 



Control Treatment for Jumbo Drills (con- 
tract HO387006, Bolt Beranek and Newman, 
Inc.). BuMines OFR 111-83, 1982, 
106 pp.; NTIS PB 83-218800. 

6. U.S. Mine Safety and Health Admin- 
istration. Noise Control Abstracts. 
Compiled by MSHA Health and Safety Tech- 
nology Centers, Denver, CO, and Pitts- 
burgh, PA, 1983, 45 pp. 

7. Dutta, P. K. , and P. W. Runstadler, 
Jr. Development of Commercial Quite Rock 
Drills (contract J0177125, Creare Pro- 
ducts, Inc. ). BuMines OFR 143-84, 1984, 
114 pp.; NTIS PB 84-232644. 

8. Dutta, P. K. , and W. N. Patterson. 
Development of Noise Control Technology 
for Jumbo Drills (contract HO395025, 
Creare Products, Inc. ). BuMines OFR 21- 
86, 1985, 67 pp. : NTIS PB 86-165081. 



35 



9. Dutta, P. K. , and W. N. Patterson. 
Development of Prototype Quiet Hard Rock 
Stoper Drill, Volume I (contract 
H0113034, Creare Products, Inc.). Bu- 
Mines OFR 128-85, 1985, 63 pp. ; NTIS 
PB 86-139722. 

10. Patterson, W. N. Development of 
Prototype Quiet Hard Rock Stoper Drill, 
Volume II (contract HOI 13034, Creare 
Products, Inc. ). BuMines OFR 20-86, 
1986, 37 pp.; NTIS PB 86-165073. 



11. Beranek, L. L. Noise and Vibra- 
tion Control. McGraw-Hill, 1971, 650 pp. 

12. Hawkes, I. , D. D. Wright, and 
P. K. Dutta. Development of a Quiet Rock 
Drill, Volume 2: Sources of Drill Rod 
Noise (contract J01 55099, Ivor Hawkes 
Associates). OFR 132-78, 1977, 77 pp.; 
NTIS PB 289 716. 



U.S. GOVERNMENT PRINTING OFFICE: 1 987 ■ 605-01 7/601 26 



INT.-BU.0F MINES,PGH.,PA. 28607 



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Bureau of Mines— Prod, and Distr. 
Cochrane Mill Road 
P.O. Box 18070 
Pittsburgh. Pa. 15236 



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